The present invention relates to a pressure sensor.
German Published Patent Application No. 43 34 123 describes a pressure sensor, in which a sensor casing containing a semiconductor pressure pickup such as a silicon chip is mounted on a printed circuit board as an SMD (surface mounting device) component. The sensor casing has a bottom part and a cover part, with a pressure connection being integrally molded on the bottom part of the sensor casing, this pressure connection having a connector for a pressure tubing, and a pressure channel arranged therein through which pressure can act on the semiconductor pressure pickup. With the known pressure sensor devices, the pressure connection is part of the sensor casing, so the sensor casing is always mounted together with the pressure connection on the mounting rack in assembling the sensor casing. In assembling other SMD components, the pressure connection projecting away from the mounting rack is often an obstacle. Another disadvantage is that it is impossible to perform a visual inspection of the soldered joints after establishing the electrical connection between the terminals of the sensor casing and the printed circuit board, because the respective instruments cannot be brought close enough to the soldered joints because of the pressure connection.
Customers have demanded that the connector for the pressure sensor projects either at the top or bottom of the mounting rack. Different demands are also made regarding the shape and design of the connector. With the known devices, the pressure connector is part of the sensor casing, so various complete systems with casing, pressure connector, semiconductor pressure pickup and all other components must be kept in stock for the different applications.
The disadvantages of the related art are avoided with the pressure sensor according to the present invention. With the device according to the present invention, the pressure connector is designed as a molded part produced independently of the sensor casing and securable on the mounting rack, where an outlet of the pressure channel designed on the molded part is connected at least indirectly to an opening in the sensor casing. This feature yields the advantageous result that the sensor casing can be mounted on the mounting rack independently of the pressure connector. Thus, sensors which are relatively simple to manufacture can be used to advantage, their very flat sensor casing having a carrier board and a cover part mounted on the carrier board with a bore provided in the cover part. Such sensors which are available for use as barometers do not have a pressure connector and can be acquired from the manufacturers relatively inexpensively. After automatic assembly and soldering of the sensor casing on the mounting rack, the soldered joints can be checked conveniently and additional SMD components and other components can be assembled on the mounting rack unhindered. After completion of the mounting rack, the pressure connector is attached to the mounting rack in such a way that the outlet of the pressure channel designed on the pressure connector is connected directly or indirectly to the opening of the sensor casing. This advantageously prevents damage to the pressure connector in soldering components to the mounting rack. In addition, securing the pressure connector to the mounting rack yields a simple and also very reliable method of mounting the pressure connector, because it is not attached merely to the sensor casing. This measure prevents a load from being applied to the soldered joints of the sensor when the pressure tubing is attached.
Thus, the connection between the pressure channel of the pressure connection and the opening in the sensor casing can be sealed easily by a sealing part arranged between the outlet of the pressure channel and the opening in the sensor casing. For this reason, the pressure connection may have a recess surrounding the outlet of the pressure channel with the sealing part inserted into this recess.
Fastening devices each designed as a locking device may advantageously be provided on the pressure connection for securing the pressure connection on the mounting rack. It is especially advantageous if the locking device can be engaged in recesses in the mounting rack in an insertion direction running perpendicular to the top side of the mounting rack provided with the sensor casing.
If the opening, in the sensor casing is arranged on the top side of the sensor casing facing away from the mounting rack, and if the outlet of the pressure channel is designed on a section of the pressure connection facing the mounting rack, then the sealing ring can advantageously be clamped between the sensor casing and the pressure connection in connecting the pressure connection. Therefore, the pressure connection has at least one elastically deformable spring arm which presses the sealing part against the sensor casing.
In another embodiment, the connector of the pressure connection is designed with an angle bend and passed through a passage in the mounting rack to the underside of the mounting rack facing away from the sensor casing. It is advantageous that this does not require modification of the sensor casing.
The pressure connection may advantageously be made of plastic, e.g., as a simple injection molded part.